The present invention relates to a plasma processing apparatus and a method of cleaning the apparatus, and especially to a plasma processing apparatus for performing processes such as plasma etching, ion-doping, plasma-CVD film formation, sputtering film formation, and so on, which are used in the fabrication of semiconductor, and to a cleaning method for removing deposits adhering to the inside wall of the apparatus while the processes are performed.
A plasma processing apparatus used for fabricating semiconductor requires a high production rate, a high-speed fabrication of substrates, the ability to uniformly process a large-size substrate, and so forth. Many conventional techniques for a plasma processing apparatus to perform etching, CVD, etc., are disclosed in Japanese Patent Applications Laid-Open Hei 8-106994, Hei 8-92748, and Hei 6-275600. These techniques are devised to be used mainly for a CVD apparatus, and have features particular to a plasma-generation method of forming films and cleaning CVD apparatuses.
However, in all of the film formation and apparatus cleaning techniques, only the type of gas used is different: the plasma-generation and control methods are the same. Although the technique disclosed in Japanese Patent Application Laid-Open Hei 8-106994 can partially change the distribution of a magnetic field for generating plasma by changing the level of current flowing in magnet coils, deposits adhering to the inside of a plasma processing apparatus cannot be entirely removed, or places remain where the deposits have only slightly been removed, because the distribution of the magnetic field cannot be significantly changed. Further, while the technique disclosed in Japanese Patent Application Laid-Open Hei 8-92748 can clean the whole inside wall of a plasma processing apparatus, the cleaning speed is low, which is a bottleneck to the mass production of films, because the plasma enclosing ability is low near the inside wall. Furthermore, in Japanese Patent Application Laid-Open Hei 6-275600, there is a problem in which the low cleaning ability of the multi-cusped magnetic field generating means may actually cause contamination of the inside wall of a processing apparatus.
Recently, since the capacities of semiconductor memory cells have been hugely increased, and their patterns are also made very minute, the reduction of particles generated in plasma during the processing of semiconductor memory cells has become indispensable from a production yield point of view. Particles of the material from which a film is made adhere not only to the surface of a substrate but also to the substrate-electrode, the inside wall of the processing chamber, the internal systems, etc. These adhering particles of the material from which a film is made are further detached and float in the processing chamber due to the injection of gas, vacuum ventilation, heating/cooling, an electrical discharge to generate plasma, and so on. Further, these particles enter the formed film.
Therefore, the adhering particles are removed by cleaning the inside wall of the processing chamber between film formation processes, or after finishing a predetermined intermediate sequence of a film formation process. However, particles adhering to some places are only slightly removed due to effects of either a magnetic field generating plasma, or an electric field.